The present invention relates to devices for enhancing the repeatibility of consistent regulated fluid discharges and, more particularly, to discharge tubes and a method of enhancing the repeatability of regulated fluid discharges therefrom.
Devices such as non-contacting tonometers are known to require consistently repeatable regulated fluid discharges. Conventional non-contacting tonometers have a plenum chamber to receive an air pulse and a discharge tube connected to the plenum chamber for directing the air pulse toward an eyeball. The objective carrying the discharge tube of the only commercial embodiment of such devices is shown in FIG. 1. This objective has been used on commercial instruments since 1972 and has a fluid discharge tube which terminates at the junction of the tube and the objective shoulder.
Tonometer housing 1 has air passage 2 for delivering compressed air to plenum chamber 3. Plenum chamber 3 comprises a bore having stepped cylindrical walls 4, 5 and 6 with the diameter of wall 4 being less than the diameter of wall 5 which, in turn, is less than the diameter of wall 6. One end of the plenum chamber 3 is defined by window 7 which is cemented to surface 8 of housing 1. Wall 6 is defined by a portion of objective body 9. The other end of plenum chamber 3 is defined by lens surface 10 of objective doublet 11. Discharge tube 12 extends from the plane of shoulder 15 of lens retaining ring 16 through doublet 11 and front lens 13 to direct an air pulse from plenum chamber 3 toward a patient's eye (not shown). Interior wall 14 of discharge tube 12 is usually highly polished to a uniform diameter.